Apparatus and methods for acoustic signaling in subterranean...

Wells – Processes – With indicating – testing – measuring or locating

Reexamination Certificate

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C166S063000, C181S117000

Reexamination Certificate

active

06321838

ABSTRACT:

TECHNICAL FIELD
The present inventions relate to improvements in apparatus and methods used to transmit acoustic signals in subterranean wells. More particularly the present inventions relate to improved apparatus and methods for transmitting an acoustic pulse downhole and reducing the attenuation of the acoustic pulse.
BACKGROUND OF THE INVENTIONS
Acoustic signals, broadly defined, are mechanical waves that can travel through a fluid or solid. An acoustic pulse can be described in terms of the sum of superimposed sinusoidal waves of appropriate frequencies and amplitudes. Acoustic pulses may consist of low frequency or high frequency components or a combination of both.
It is known to use acoustic systems and methods for performing operations in a gas or oil well. Generally, acoustically controlled working apparatus is deployed downhole and acoustic pulses are transmitted into the well. An acoustic pulse can be sent down a fluid filled tube to remotely control a downhole device designed to respond to an acoustic pulse or predetermined series of pulses. One of the problems with transmitting acoustic signals downhole is the attenuation of the acoustic signal. Acoustic signals transmitted into a well tend to decay exponentially with distance, making the use of such systems particularly difficult with increased depth. One method of attempting to overcome the attenuation problem is the use of acoustic repeaters. The repeaters must be spaced at various depths along the well, creating problems of cost and complexity.
Because of the above problems, there is a need for improved apparatus methods of transmitting acoustic pulses downhole in a subterranean well.
SUMMARY OF THE INVENTIONS
The disclosed apparatus and methods for enhancing the propagation of acoustic signals through well tubing makes use of a vent port in the tubing wall between the source of an acoustic pulse and the intended receiver. In general, the vent port has an open chamber to vent excess pressure while retaining the desired frequency components of the acoustic pulse. The vent port and chamber are proportioned relative to one another and to the well tubing diameter to perform the venting function without dramatically attenuating the desired low frequency components of the acoustic pulse.
According to one embodiment of the apparatus and methods, the invention transmits acoustic signals downhole through well tubing with a compressed gas gun.
According to another embodiment of the apparatus and methods of the invention acoustic pulse transmissions from a compressed gas gun are used to control one or more downhole tools.


REFERENCES:
patent: 3900827 (1975-08-01), Lamel et al.
patent: 4293936 (1981-10-01), Cox et al.
patent: 5293937 (1994-03-01), Schultz et al.
patent: 5443119 (1995-08-01), Chambers et al.
U.S. Patent application Ser. No. 09/056,053, filed Apr. 6, 1998.
U.S. Patent application Ser. No. 09/056,055, filed Apr. 6, 1998.
Copy of Kinsler, L. E., Frey, A. R. Coppens, A. B. and Sanders, J. V.Fundamenttals of Acoustics, John Wiley & Sons, Inc., 1982, pp. 239-241.
Copy of Mauer, W. C., MacDonald, W. J., Shoemaker, H. D., Dareing, D. W., “Mud Pulse Tachometer For Downhole Drilling Motors”, 81-pet-3, Presented at the ASME Energy Sources Technology Conference and Exhibition, Jan. 18-22, 1981, Houston, Texas.
Copy of Patton, B. J., Gravely, J. K., Sexton, J. H., Hawk, D. E., Slover, V. R., Harrell, J. W., “Development and Successful Testing of A Continuous-Wave, Logging-While-Drilling Telemetry System”,Journal of Petroleum Technology, Oct., 1977, p. 1215-1221.

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